But people in some northern neighborhoods of Rancho Cucamonga were urged to leave voluntarily if they felt threatened, and the winds still were too high to permit aircraft to battle the flames, said Chon Bribiescas, a spokesman for the U.S. Forest Service.

The blaze erupted around 8 a.m. in the foothills of the San Bernardino National Forest and by afternoon had burned 1,000 acres of brush.

The flames leapt through rocky brushlands, some of which last burned a decade ago. Hot, dry winds gusting to 70 mph or more at times sent smoke and ash over some neighborhoods.

Even where homes weren't in imminent danger, the threat remained.

A blaze fanned by gusts "tends to throw embers and brands ahead of itself, sometimes a mile," Bribiescas said. "That's the insidious part of a wind-driven fire."

At the fire's height, seven schools were closed and parents scrambled to take their children away.

Golden Elementary School was placed under voluntary evacuation.

Francisco Aguilar, a Los Angeles city firefighter who lives in Rancho Cucamonga, picked up his 11-year-old daughter, Bella.

"It's like a madhouse in there," he told the San Bernardino Sun (http://bit.ly/1fzZX8Y ). "Parents are running around trying to grab their kids, and kids are covering their faces with tissue or their T-shirts."

Leo Lemelin, 67, and his family busily loaded several cars with belongings as they prepared to leave.

"We're trying to pack up everything we can into our cars from 45 years of marriage and eight grandchildren," he told the Riverside Press-Enterprise (http://bit.ly/1ftmqok).

About 700 firefighters battled the wildfire. But they were bereft of air support as afternoon wind gusts of 70 mph per hour or more grounded the low-flying planes and helicopters.

"We tried early on, but it was just too dusty" to safely put the craft into the sky, John Miller of the U.S. Forest Service said at an afternoon press conference.

The winds finally began to ease in late afternoon, and the mandatory evacuation was cancelled shortly before 6 p.m.

Although the fire remained out of control, it had run out of fuel in some areas, while firefighters and bulldozers cut away brush in others, Bribiescas said.

The only structure that burned was a fence, he said.

The winds were expected to continue easing overnight, but they could pick up again Thursday.

The National Weather Service issued a red-flag warning of extremely dangerous fire conditions in Los Angeles, Orange and Ventura counties until 8 p.m. Thursday.

The winds also fanned a handful of small brush fires around Southern California on Wednesday that were quickly doused without damage.

At one point, utilities reported about 8,000 people had lost power because of wind-related problems such as downed power lines.

The fire erupted in the midst of a heat wave that sent Southern California temperatures soaring into the 90s in some areas.

Los Angeles International Airport recorded a high of 87 degrees, breaking the record for the day of 86 that was set in 1996. At Long Beach Airport, the high of 92 broke a 1996 record by 2 degrees.

High temperatures were expected through Saturday, with humidity in the single digits.